Digital BW, The Print

In a message dated 5/8/02 3:30:52 PM, dickbo@... writes:

>> Yes, removing the neutral component from a mixed value should be referred
>
>to
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>> as gray component replacement... no matter how I was taught...
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>
>
>Smartly put if I might say so because, as I am sure you will already know,
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>it is all but impossible to define where a neutral leaves off and something
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>else begins - that being the assumption behind the old gravure technique
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>known to one and all as Under Colour Removal.

Yes, and when one writes the software, then the names mean what one wants 
them to mean... I've had an ongoing discussion with programmers for various 
RIPs and color software over what to call proprietary processes in this area.
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>
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>GCR on the other hand - as I am quite sure you will know - merely requires
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>the programmer to identify the least colour component in any given three
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>colour area and exchange it for black- and that is perfectly possible to
>do,
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>is done and works admirably by saving ink, making press colour register
>more
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>straight forward and indeed it is claimed makes the resultant image look
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>sharper because of better colour to colour register.

Assuming that gray is actually represented by C=M=Y, life can be this simple. 
Unfortunately, if gray for a given printer, settings, inkset and paper is 
represented by C128, M 144, Y 166, then removing only 128 from each of the 
three, and replacing it with K will get you something you may not be 
expecting!

>
>But I am sure you already know all of that very old information so I must
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>apologise for burdening you with a history lesson.
>
>By the way, how does the old epson six colour handle such matters forsooth?

That depends on the Epson... but before the encapsulated inks reared their 
metameric heads, the fixed black generation used mostly CMY until *very* 
close to black, then made a very sharp transition to 100%K for black. This 
trend is very much reversed with the newer pigment drivers, where as much CMY 
as possible is removed, right into the highlights, and replaced with K. This 
is fine for the 5500, with its invisibly fine black dots, but for other 
piment printers the result is varying degrees of black graininess in the 
lighter tones. The newest Epsons will fix this with light K (gray) ink for 
use in the lighter areas. 

C. David Tobie
Design Cooperative
CDTobie@...